1. Field of the Invention
The present invention relates generally to a method of controlling an imaging apparatus by detecting a moving characteristic of a mechanical shutter and an imaging apparatus using the same, and more particularly, to a method of controlling an imaging apparatus, which calculates a moving characteristic of a mechanical shutter and controls an electronic shutter operation of an image sensor according to the calculated moving characteristic of the mechanical shutter, and an imaging apparatus using the same.
2. Description of the Related Art
Camera shutters are generally classified as lens shutters and focal plane shutters. A lens shutter is located in the proximity of a lens, whereas a focal plane shutter is located in the proximity of a focal surface.
The focal plane shutter is classified into two types, i.e., a horizontal shutter and a vertical shutter, according to moving directions of front and rear curtains. Currently, the vertical shutter is commonly used because of good performance.
A subject that is incident on an imaging surface through a lens is exposed to light, as the two curtains including the front curtain and the rear curtain are moving. That is, light exposure begins as the front curtain moves and the imaging surface of the imaging apparatus is opened, and a photographing operation finishes as the rear curtain moves, after a predetermined time elapses according to a pre-set shutter speed.
However, because the front and the rear curtains are configured mechanically, the front curtain may collide with a shutter substrate when the front curtain finishes moving and may cause a collision vibration, which is commonly referred to as a front curtain shock. Because the front curtain shock occurs when the imaging surface is initially exposed to the light, the vibration on the imaging surface has a bad influence on an overall photographing operation. However, because the rear curtain moves when the photographing operation finishes, the vibration caused by the rear curtain has almost no influence on the photographing operation.
Also, because the front curtain should be always charged in order to photograph in a live view mode, a temporal gap, i.e., a release time lag, occurs.
In order to remove such effects of the front curtain, a technique for electronically processing the front curtain of the focal plane shutter has been proposed. This technique simulates the function of the front curtain by scanning pixels in a sequence on a pixel row basis using a reset signal that indicates a beginning of light exposure for each pixel in an image sensor of an imaging apparatus, such as a Charge-Coupled Device (CCD) or a Complementary Metal-Oxide Semiconductor (CMOS) Image Sensor (CIS). In other words, the mechanical front curtain is replaced by electronically controlling a reset signal of an image sensor, while a rear curtain moves in an existing mechanical method.
However, mechanical characteristics, such as a change in a curtain speed due to the changes in temperature, humidity, and posture of the camera, and different curtain speeds at the beginning point and the finishing points may appear because the rear curtain still uses the mechanical method. In this case, if the front curtain also uses the mechanical method, there is no problem because the front and the rear curtains maintain the same mechanical characteristics. However, if the front curtain is replaced with an electronic method, as described above, the moving characteristic of the electronic front curtain and the moving characteristic of the mechanical rear curtain are not identical to each other, which causes vignetting and deteriorates the performance of the imaging apparatus.